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Antarctic Temperature and Snowfall in a Warming World
Volume 11, Number 43: 22 October 2008

In the September 2008 issue of the Bulletin of the American Meteorological Society, Monaghan and Bromwich (2008) review what has been learned about snowfall and near-surface air temperature over the past five decades in Antarctica. This they do because, in their words, "snowfall is the largest contributor to the growth of the ice sheets, and near-surface temperature controls surface melting, which in turn has important impacts on the stability of Antarctic ice shelves and glaciers," which ultimately, we might add, impact global sea level.

So what did their review reveal?

The two researchers from the Byrd Polar Research Center of Ohio State University (USA) begin by noting that "instrumental records indicate statistically insignificant seasonal and annual near-surface temperature changes over continental Antarctica from the late 1950s through 2000," citing the work of Turner et al. (2005). On the Antarctic Peninsula, on the other hand, temperature measured at the Faraday/Vernadsky station rose at the phenomenal rate of 0.56C per decade from 1951 to 2000. However, the peninsula comprises a mere 4% of the continent's total surface area; and its warming, although dramatic, is thus but a small-scale anomaly.

In describing another study of the temperature history of Antarctica, Monaghan and Bromwich report that "Chapman and Walsh (2007) performed an objective analysis of Antarctic near-surface temperatures from the early 1950s through 2002 and found that the overall Antarctic temperature trends depend on the period for which they are calculated, being positive prior to 1965 (through 2002), and mainly negative thereafter, although never statistically significant for any period." Similarly, after citing the work of Kwok and Comiso (2002) with skin temperature records derived from Advanced Very High Resolution Radiometer instrumentation flown aboard polar-orbiting satellites, the work of Schneider et al. (2006) with temperatures derived from ice-core stable isotopes, and the work of Monaghan et al. (2008) that blended the instrumental temperature record with model reanalysis temperature fields, they concluded that "overall there have not been statistically significant Antarctic near-surface temperature trends since the International Geophysical Year" of 1957-58.

Turning their attention to snowfall, Monaghan and Bromwich note that "atmospheric models have been the primary tool for assessing temporal variability," and they report that the latest such studies of Antarctic snowfall "indicate that no statistically significant increase has occurred since ~1980," citing the analyses of Monaghan et al. (2006) and van de Berg et al. (2005), although there have been cyclical changes related to similar changes in temperature. And when the two variations are compared on decadal time scales, it appears that snowfall over Antarctica could possibly rise by as much as 5% for each 1C increase in temperature.

So what might the future hold for Antarctic snowfall in a warming world?

The two researchers say that "if global climate model projections of 2-3.5C temperature increases over Antarctica by the end of this century are accurate" -- which is something that is highly debatable -- "a ~10%-20% increase in snowfall might be expected if the 1960-2004 sensitivity relationship holds." And in this regard, they note that "a 15% increase of Antarctic snowfall would mitigate [our italics] an additional ~1 mm per year [rise] of global sea level in 2100 compared to today."

When all is said and done, therefore, the fantastic multi-meter rise in sea level predicted by Al Gore and James Hansen to occur this century appears to be pure fantasy, and even more so, in light of Monaghan and Bromwich's ultimate observation that "a widespread signal of Antarctic climate change is not obvious over the past ~50 years."

Sherwood, Keith and Craig Idso

References
Chapman, W.L. and Walsh, J.E. 2007. A synthesis of Antarctic temperatures. Journal of Climate 20: 4096-4117.

Kwok, R. and Comiso, J.C. 2002. Spatial patterns of variability in Antarctic surface temperature: Connections to the Southern Hemisphere Annular Mode and the Southern Oscillation. Geophysical Research Letters 29: 10.1029/2002GL015415.

Monaghan, A.J. and Bromwich, D.H. 2008. Advances in describing recent Antarctic climate variability. Bulletin of the American Meteorological Society 89: 1295-1306.

Monaghan, A.J., Bromwich, D.H., Chapman, W. and Comiso, J.C. 2008. Recent variability and trends of Antarctic near-surface temperature. Journal of Geophysical Research 113: 10.1029/2007JD009094.

Monaghan, A.J., Bromwich, D.H. and Wang, S.-H. 2006. Recent trends in Antarctic snow accumulation from Polar MM5 simulations. Philosophical Transactions of the Royal Society A 364: 1683-1708.

Schneider, D.P., Steig, E.J., van Ommen, T.D., Bitz, C.M., Dixon, D.A., Mayewski, P.A. and Jones, J.M. 2006. Temperatures in Antarctica over the past two centuries. Geophysical Research Letters 33: 10.1029/2006GL027057.

Turner, J., Colwell, S.R., Marshall, G.J., Lachlan-Cope, T.A., Carleton, A.M., Jones, P.D., Lagun, V., Reid, P.A. and Iagovkina, S. 2005. Antarctic climate change during the last 50 years. International Journal of Climatology 25: 279-294.

van de Berg, W.J., van den Broeke, M.R., Reijmer, C.H. and van Meijgaard, E. 2005. Characteristics of the Antarctic surface mass balance (1958-2002) using a regional atmospheric climate model. Annals of Glaciology 41: 97-104.